Human cytomegalovirus (HCMV) infection in utero is an important cause of central nervous system damage in newborns. Although the virus is widely distributed in the population, about 40% of women enter pregnancy without antibodies and thus are susceptible to infection. About 1% of these women undergo primary infection in utero. Classical cytomegalic inclusion disease is rare; however, a proportion of the infected infants, including those who were symptom free, are subsequently found to be mentally retarded (Lancet Jan. 5, 1974, pp. 1-5).
Preliminary estimates based on surveys of approximately 4,000 newborns from several geographical areas indicate that the virus causes significant damage of the central nervous system leading to mental deficiency in at least 10%, and perhaps as high as 25%, of infected infants. Assuming that about 1% of newborn infants per year excrete HCMV and that about one fourth of those develop mental deficiency, in the United States this means approximately 10,000 brain-damaged children born per year. This is a formidable number, particularly in view of the ability of these children to survive (J. of Infec. Dis. 123, No. 5,555 (May, 1971)).
Many serological tests have been suggested for the determination of HCMV antibody. Of these, the immunofluorescent test is the most rapid, sensitive and convenient. Unfortunately, technical difficulties have been encountered in the preparation of target cells for use in the latter test. These difficulties are based on the fact that human fibroblasts, which heretofore have been used as the target cells, have a limited life span. Thus, it has been necessary to use human fibroblasts freshly infected with HCMV when preparing target cells. Since the infectivity of HCMV inocula is not stable even when preserved at -70.degree. C., it is difficult to obtain a predictable number of infected cells in each preparation.